Improving source/drain contact resistance of amorphous indium-gallium-zinc-oxide thin-film transistors using an n+-ZnO buffer layer

To avoid high temperature annealing in improving the source/drain (S/D) resistance (RDS) of amorphous indium-gallium-zinc-oxide (alpha-IGZO) thinfilm transistors (TFTs) for flexible electronics, a simple and efficient technique using a sputtering-deposited n(+)-ZnO buffer layer (BL) sandwiched between the S/D electrode and the alpha-IGZO channel is proposed and demonstrated. It shows that the RDS of alpha-IGZO TFTs with the proposed n(+)-ZnO BL is reduced to 8.1 x 10(3)Omega as compared with 6.1 x 10(4)Omega of the conventional one. The facilitation of carrier tunneling between the S/D electrode and the alpha-IGZO channel through the use of the n(+)-ZnO BL to lower the effective barrier height therein is responsible for the RDS reduction. Effects of the chamber pressure on the carrier concentration of the sputtering-deposited n(+)-ZnO BL and the thickness of the BL on the degree of improvement in the performance of alpha-IGZO TFTs are analyzed and discussed. (C) 2016 The Japan Society of Applied Physics